[Akuma]

If you're OCed, turn it way down.

[url=http://www.memtest86.com:f35ab]Download memtest86[/url:f35ab] and run it, it will tell you if there is anything wrong with your RAM.

If that passes, then it's software that is causing it. Firefox has a minor memory leak that peaks around 400mb but it wouldn't cause your computer to reboot and give you an error message. It would just be choppy for a few seconds until it returned to normal.